DESCRIPTION: Dr. Minden has tools to monitor the developmental fates of cells emerging from mitotic domains. These domains are composed of synchronously dividing clusters of cells in the blastoderm, which appear to prefigure development of specific regions of the embryo. He has developed gene expression and cell death markers for use in time-lapse studies of live, developing embryos. Central to these studies has been production of a "caged" form of GAL4VP16. This involves a photoreversible chemical modification of the protein. Exposure of GAL4VP16 to 6-nitroveratrylchloroformate, which modifies lysine, was shown to block DNA binding in vitro. The modified protein is injected into pre-blastoderm embryos, and can be photoactivated by UV illumination at the level of single cell targets. He proposes to map the fates of all cells composing the 12 mitotic domains contributing to the procephalic region. With such maps in hand, further mapping will be carried out to determine patterns of cell death within the mapped domains.